1. Field of the Invention
The invention relates to a torque detection device including: a magnetic flux collecting unit that includes a holder that has a holding protrusion and a through-hole located next to the holding protrusion, a magnetic flux collecting ring fitted to the inner periphery of the holder, and a magnetic shield fitted to the outer periphery of the holder so as to cover the through-hole; and a sensor housing formed integrally with the magnetic flux collecting unit by supplying resin onto the outer periphery of the magnetic flux collecting unit, and relates also to an electric power steering system (EPS) that includes the torque detection device.
2. Discussion of Background
A torque detection device described in US2010/0071481 A1 includes a unit that has magnetic flux collecting rings and a ring holder that holds the magnetic flux collecting rings. The unit is inserted into a housing through an insertion hole formed in the housing, and is fixed to the housing.
For example, water may enter the inside of the torque detection device described in US2010/0071481 A1 through a gap between the unit and the housing. There is a torque detection device in which a sensor housing is formed integrally with a magnetic flux collecting unit by supplying resin onto the outer periphery of the magnetic flux collecting unit in order to improve the waterproof property. The magnetic flux collecting unit includes a holder, magnetic flux collecting rings and a magnetic shield. The holder has holding protrusions formed on its inner periphery and through-holes located next to the holding protrusions. The magnetic flux collecting rings are fitted to the inner periphery of the holder. The magnetic shield is fitted to the outer periphery of the holder so as to cover the through-holes.
However, in process of supplying resin, portions of the magnetic shield, which face the through-holes, may deform due to resin pressure. This decreases the accuracy of calculation of a torsion angle of a torsion bar, which is executed by the torque detection device on the basis of an output from a magnetic sensor.